Jammer wrote: You seem to be stating that all cubits were definitely equal over the duration of the OK constructs. Can you link to the supporting documentation of this?

Absolutely not, there were several cubit lengths as shown by Petrie's survey, there are a minimum of at least 2 different cubits in G1, demonstrating they did not use a uniform cubit length for each construction.

[www.ronaldbirdsall.com]

"For the value of the usual cubit, undoubtedly the most important source is the King's Chamber in the Great Pyramid; that is the most accurately wrought, the best preserved, and the most exactly measured, of all the data that are known. The cubit in the Great Pyramid varies thus:—
By the base of King's Chamber, corrected for opening of joints 20.632 ± .004
By the Queen's Chamber, if dimensions squared are in square cubits 20.61 ± .02
By the subterranean chamber 20.65 ± .05
By the antechamber 20.605 ± .032
By the ascending and Queen's Chamber passage lengths (section 149) 20.58 ± .02
By the base length of the Pyramid, if 440 cubits (section 143) 20.622 ± .002
By the entrance passage width 20.622 ± .002
By the gallery width 20.765 ± .01

The passage widths are so short and variable that little value can be placed on them, especially as they depend on the builder's and not on the mason's work. The lengths of the passages are very accurate data, but being only single measures, are of less importance than are chambers, in which a length is often repeated in the working. The chamber dimensions are rather variable, particularly in the subterranean and Antechamber, and none of the above data are equal in quality to the King's Chamber dimensions. If a strictly weighted [p. 179] mean be taken it yields 20.620 ± .004; but taking the King's Chamber alone, as being the best datum by far, it nevertheless contracts upwards, so that it is hardly justifiable to adopt a larger result than 20.620 ± .005."

There is a difference between wandering and intentional use of different length cubits.
In “The Pyramids Of Egypt” by Livio C. Stecchini he states: “There is a famous text of Egyptian geography which is found inscribed on three different measuring rods and of which other copies seem to exist. Even though the rods are of later periods the text of the inscription is considered to have been drafted in the Old Kingdom because of its linguistic style. The text says that from Behdet to the Apex of the Delta there are 86 schoinoi. Egyptologists have not been able to make sense out of this text, because they have declared a priori that a calculation in terms of differences of latitude was impossible. Hence, they have dismissed these documents as gibberish without even trying to test their figures in terms of latitude.”

Stecchini was correct in his assertion, but we will clumsily try to comprehend by using a one size fits all cubit when it does not exist.